Dog Breeds
There are numerous dog breeds, with over 800 being recognized by various kennel clubs worldwide. As all dog breeds have been derived from mixed-breed dog populations, the term "purebred" has meaning only with respect to a certain number of generations. Many dogs, especially outside the United States of America and Western Europe, belong to no recognized breed.
The Papillon breed is highly athletic breed of dogA few basic breed types have evolved gradually during the domesticated dog's relationship with man over the last 10,000 or more years, but most modern breeds are of relatively recent derivation. Many of these are the product of a deliberate process of artificial selection. Because of this, some breeds are highly specialized, and there is extraordinary morphological diversity across different breeds. Despite these differences, dogs are able to distinguish dogs from other kinds of animal.
The definition of a dog breed is a matter of some controversy. Depending on the size of the original founding population, closed gene pool breeds can have problems with inbreeding, specifically due to founder effect. Dog breeders are increasingly aware of the importance of population genetics and of maintaining diverse gene pools. Health testing and new DNA tests can help avoid problems, by providing a replacement for natural selection. Without selection, inbreeding and closed gene pools can increase the risk of severe health or behavioral problems. Some organizations define a breed more loosely, such that an individual may be considered of one breed as long as 75% of its parentage is of that breed. These considerations affect both pets and the show dogs entered in dog shows. Even prize-winning purebred dogs sometimes possess crippling genetic defects due to founder effect or inbreeding.[23] These problems are not limited to purebred dogs and can affect mixed-breed populations.[24] The behavior and appearance of a dog of a particular breed can be predicted fairly accurately, while mixed-breed dogs show a broader range of innovative appearance and behavior.
Mixed-breed dogs or Mongrels are dogs that do not belong to specific breeds, being mixtures of two or more in variant percentages. Mixed breeds, or dogs with no purebred ancestry, are not inherently "better" or "worse" than purebred dogs as companions, pets, working dogs, or competitors in dog sports. Sometimes mixed-breed dogs are deliberately bred, for example, the Cockapoo, a mixture of Cocker Spaniel and Miniature Poodle. Such deliberate crosses may display hybrid vigor and other desirable traits, but can also lack one or more of the desired traits of their parents, such as temperament or a particular color or coat. However, without genetic testing of the parents, the crosses can sometimes end up inheriting genetic defects that occur in both parental breeds. Deliberately crossing two or more breeds is also a manner of establishing new breeds.
